Last week I had a similar looking problem. Query v$session_wait and see
if you are waiting on any latches. I found I was waiting for a library
cache pin (for several hour).

The fix was to identify the process holding the latch and kill it.
MetaLink gives some information on how to identify a process holding a
latch (the v$ views do not, as it is never supposed to be held long
enough to do you any good). Unfortunately, I don't have the exact query
I used right at hand.

Another thought: Did you forget to kill the o/s process behind that
Oracle process? =20